Zoella (Zoe Sugg) at a book signing for debut novel Girl Online in November. Photograph: Bluewater/REX

YouTube star Zoe Sugg has announced that she is taking a break from the internet after admitting that she did not write her bestselling debut novel alone. Sugg took to her Twitter account, where she has 2.61 million followers, to ask fans to “Bare [sic] with me on vlogmas. I’m taking a few days out and off the internet because it’s clouding up my brain. Thanks for understanding.”

Sugg, whose videos on YouTube about fashion and beauty have won her more than 5 million subscribers, shot to the top of bestseller charts when Girl Online was published last month. It sold 78,109 copies in its first week, the biggest recorded first-week sale for a debut, according to the Bookseller.

The story, about an anonymous teenage blogger who has a relationship with a US pop star, “touches on many issues Zoe talks about in her videos and blogs – such as dealing with panic attacks and juggling separate online and offline lives”, said her publisher, Penguin, earlier this year, and is “told in Zoe’s relatable, fresh and engaging voice”.

But after sustained pressure over whether or not the book was ghostwritten by Siobhan Curham, who is named in the acknowledgements, Sugg posted a statement on Sundaylate Sunday afternoon, saying that, “for the doubters out there, of course I was going to have help from Penguin’s editorial team in telling my story, which I talked about from the beginning”.

“Everyone needs help when they try something new,” added Sugg. “The story and the characters of Girl Online are mine.”

Sugg’s temporary departure from the internet is a radical statement for the Youtube star, whose popularity is built almost entirely on her online presence and updates her Twitter and other social media at least once a day.

A statement from Penguin on Monday said that, “as publishers our role is, and always has been, to find the very best talent and help them tell their story and connect them with readers”.

“Talented You Tube entrepreneurs such as Zoe are brilliant at understanding and entertaining their audience. For her first novel, Zoe has worked with an expert editorial team to help her bring to life her characters and experiences in a heartwarming and compelling story … We are proud to be have been able to help Zoe tell her story and that the book is proving so successful in getting young people reading,” said the publisher.

A spokesperson for Penguin told the Sunday Times: “To be factually accurate, you would need to say Zoe Sugg did not write the book Girl Online on her own”. And the publisher added commented to the Bookseller[http://www.thebookseller.com/news/penguin-zoella-had-help-girl-online]: “Siobhan was part of the editorial team … As with many new writers [Sugg] got help in bringing that story to life. If you read the book, it is clearly Zoe’s story and an expression of herself.”

When Penguin announced that it had signed up Sugg earlier this year, it said that the vlogger had “written her debut novel in close collaboration with Penguin Children’s editorial director Amy McCulloch and editorial consultant Siobhan Curham”. Curham is also thanked in the acknowledgments of the novel by Sugg, who writes that she was “with me every step of the way”, and Penguin said the vlogger also made “this help clear in her thank yous at her launch party, in a room full of journalists”.

Curham did not respond to a request for comment on Monday morning, but has thanked commenters online for remarks from supporters including “really hope you’re OK right now – you deserve all the credit, and I find the whole thing misleading and awful”. The author of novels for adults and teenagers, as well as non-fiction, she says on her website that she is also an editorial consultant in children’s publishing, helping create a range of fiction series. On Amazon, Curham’s biography describes her as “the editorial consultant and writing coach for Zoe Sugg (Zoella), the YouTube vlogger and author of the bestselling blockbuster Girl Online series”. In a blog by Curham posted on GoodReads in August, but since deleted from her own website, she writes of how she was “asked this year by a publisher if I could write a book for them and oh yes, please could I write it in six weeks … aaaaaand … I did it! I wrote an entire 80,000 word novel in six weeks.” The novel is not named, but speculation online suggested it was Girl Online, although Penguin denied this to the Telegraph.

The acknowledgement that Sugg did not write the novel on her own has upset some fans, one blogging that “I suppose Zoe has never actually claimed that she wrote the book herself, but surely the act of putting only her name on the cover implies that she did? Surely accepting congratulations over a book well-written without ever mentioning another writer implies that she did?”

It has also prompted some backlash on Amazon, where reviews of the novel now include the comment that: “I was considering purchasing this book, but today I have seen that the publishers have admitted that it was ghostwritten. I feel like this is cheating young girls out of their pocket money.”

But Sugg also has her supporters, TV presenter Dawn O’Porter writing on Twitter: “Even as a writer I feel bad for Zoella. Hardly any slebs write their own autobiographies and no one has a pop at that. She is so young … She would have been heavily involved but had a ghostwriter to actually write it. That’s not a new thing? Chill with the hate.”

“Great writing by actual great writers still exists. This is just highly marketable stuff that sells,” O’Porter added. “And don’t feel sorry for a ghostwriter who doesn’t get the credit. They took the job knowing that was the deal.”

“What people don’t get is that it is hard to write books – it takes a lot of practice,” said author and professional ghostwriter Andrew Crofts. “To expect someone who does something completely different, like football or politics or vlogging, to be able to sit down and write 80,000 words is ludicrous. Of course she’ll have needed editorial help – even expert novelists need help. This is just taking it a little further, and [all the fuss] just seems mean-spirited.”

Reports have suggested that potential ghostwriters for Sugg’s novel were offered between £7,000 and £8,000. Crofts said: “That is the sort of money publishers offer and it’s absolute cheek. But they can get away with it because people like writing books … If Penguin did pay that they should be embarrassed.”

Crofts felt that the success of Sugg’s novel shows that “if publishers find out what people want and produce it, they get bestsellers”.

“If they publish books they love themselves and expect the rest of the world to love them too, they’re just going to starve to death. But there’s room for both, and it is no good complaining about books like this. Publishers need to find out what people want and give it to them,” he said.

Zoe Sugg is by no means the first celebrity to have been outed as not the sole creative mind behind a novel. The supermodel Naomi Campbell published Swan, her debut, in 1995, but according to rumours cited by Gilbert Adair, she had not even read it, and “had to be furnished with a 250-word synopsis in order for her to offer a credible account of its plot to journalists”. Campbell went on to admit in an interview that it was ghostwritten: “I just did not have the time to sit down and write a book”.

Kerry Katona, meanwhile, admitted to the nation on Jonathan Ross’s TV show that she hadn’t written her first novel Tough Love. “To say you wrote the book would be slightly misleading,” says Ross. “It would be completely lying,” responds Katona. “Ebury, my publishers … they approached me and first of all I said no because I’m dyslexic and there’s no way in hell I could sit down and do that. So I met up with a lady called Annie and we came up with characters and storylines and plots.”

And Victoria Beckham admitted in 2005 that “I haven’t read a book in my life”, despite having published an autobiography of her own.